Conventional ion implantation is not readily utilized to dope HgCdTe substitutionally as is the case for for Si and GaAs. Conventional implantation of almost any dopant species into relatively fragile HgCdTe results in the creation of n-type material due to implant induced lattice damage.
Another conventional method of introducing a dopant into HgCdTe for junction, contact or isolation formation relies on the introduction of a dopant into a melt and the subsequent growth of doped epitaxial layers. However, this technique has several inherent disadvantages including a difficulty in producing relatively small junctions and/or controlled junction depths and a difficulty in producing junctions in planar-type devices as opposed to mesa-type.
It is thus an object of the invention to provide a method of forming in a single crystal semiconductor material a region having a different chemical composition or concentration than a chemical composition or concentration of material surrounding the region.
It is another object of the invention to provide a processing method that produces both p-type and n-type high quality junctions within HgCdTe and similarly fragile materials such as HgCdSe and InSb.
It is another object of the invention to provide a processing method that readily produces compact, low noise junctions to create dense arrays of reduced capacitance photodiodes.
It is another object of the invention to provide a processing method that readily produces both p-type and n-type junctions within HgCdTe thereby facilitating the creation of compact and low noise HgCdTe transistors by sequentially formed p and n diffusions.
It is a still further object of the invention to provide a processing method that readily produces both p-type and n-type junctions within HgCdTe or similar fragile material and that employes a multi-step process including the formation of a cap layer over the HgCdTe or similar fragile material, the implantation into only the cap layer of the desired dopant species, and the subsequent rapid thermal diffusion of the dopant through the cap layer down to the HgCdTe surface.